This application claims priority under 35 U.S.C. 119 of Japanese Patent Application No. P2000-006073, filed Jan. 11, 2000 and Japanese Patent Application No. P2000-376914, filed Dec. 12, 2000, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display device, a terminal device, or a portable terminal.
2. Discussion of the Background
Recent increases in the size of liquid crystal display devices have expanded their market as display devices for notebook personal computers, monitors, and so on.
In conventional TN type liquid crystal display devices, the contrast of displayed image was highly dependent on viewing angle. In fact, the display is visible from only certain angles. This problem, however, is being improved through measures such as the use of viewing angle compensation film. This makes it possible to provide liquid crystal display devices with the same range of viewing angles as CRTs.
In U.S. Pat. Nos. 5,666,178 or 5,652,634, methods for broadening the viewing angle are disclosed. In these methods, in one pixel is provided with a plurality of sections, each with a different pre-tilt angle direction. Additionally, in Japanese Patent JP-A-9-5766, a method is disclosed in which a section is provided with a different pre-tilt angle direction in one pixel. In these disclosed prior art methods, the section with different pre-tilt angle direction is provided in one pixel for the purpose of broadening the viewing angle. The ratio between the areas of the sections with different pre-tilt angle directions is unique for all pixels, that is, one display, in order to prevent uneven areas from occurring. Therefore, these methods neither disclose nor suggest a method of providing a specified image that is visible when the image is viewed from a specified direction.
In Japanese Patent JP-A-61-51124 and Japanese Patent JP-A-61-51125 a device having plural display areas is disclosed. In this device, liquid crystalline molecular orientation directions on the alignment films are different on a single substrate. The display patterns of this device are typically numerical. In this device, some of the numbers (display patterns) can be seen from one direction, and the others cannot be seen from the same direction. The applications of this device intend that at least one numeral on a display pattern can be seen from a direction.
On the other hand, conversely to the above, other displays are preferably only visible from the front (i.e., they do not permit oblique viewing). This prevents secret or confidential documents from being viewed by people other than the user of the display device while the documents are being prepared or read in a public place. For example, this allows the user of such a display to read or write a document such as a personal letter, regardless of the presence of people around the user. Herein, such a technology will be denoted as xe2x80x9cviewing angle narrowing technology.xe2x80x9d
The viewing angle narrowing technologies that have been disclosed heretofore are a method of jointly using a liquid crystal display device having a liquid crystal layer for image display and a liquid crystal layer for phase difference control (JP-A-11-174489, JP-A-11-7045, JP-A-9-105958), a method of using a lens sheet (JP-A-11-84357 and others), a method of using a diffusing optical guide plate (JP-A-10-97199 and others), and so forth.
However, the above-described methods suffer from problems such as an increase in the number of parts and an insufficiently narrowed viewing angle.
Accordingly, it is an object of the present invention to provide a liquid crystal display device that displays a standard image when viewed from the front and a fixed image that is independent from an inputted image signal when viewed from another direction.
To that end, the present invention provides a liquid crystal display including a liquid crystal layer and alignment films sandwiching the liquid crystal layer, wherein surfaces of the alignment films are divided into a plurality of regions including a plurality of pixel units, and liquid crystal orientations on the alignment films in adjacent regions are different.
These regions may form a letter, or these regions may form, e.g., a visible figure.
A long side of a minimum hypothetical rectangle containing the region may be equal to or larger than 0.1 millimeter. The figure may be square.
A maximum voltage for driving the liquid crystal layer may be less than the saturation voltage of the liquid crystal layer. The maximum voltage for driving the liquid crystal layer Vm and the saturation voltage Vs have a following relation: 0.005 Vsxe2x89xa6Vmxe2x89xa60.7 Vs.
The orientation in one of the regions may be unique. The orientation of the alignment films of the same color element in one of the regions may be unique.
According to a further aspect of the present invention, there is provided a liquid crystal display including a liquid crystal layer and alignment films sandwiching the liquid crystal layer, wherein surfaces of the alignment films are divided into a plurality of regions having different orientation directions, and a ratio of the regions in at least one pixel is different from a ratio of the regions in the other pixel.
The region may form a letter, or the region may form, e.g., a visible figure.
According to a further aspect of the present invention, there is provided a liquid crystal display including liquid crystal layer alignment films sandwiching the liquid crystal layer and a driving circuit for the liquid crystal layer, wherein an image formed by the driving circuit is displayed to a front direction and a fixed image independent of the driving circuit is displayed to oblique directions.
The alignment films may have a plurality of regions where orientations of the alignment films are different.
The fixed image may be a letter. The fixed image may be a visible figure. The fixed image may have a color.
According to a further aspect of the present invention, there is provided a liquid crystal display including liquid crystal layer alignment films sandwiching the liquid crystal layer and a driving circuit for the liquid crystal layer, wherein an image formed by the driving circuit is displayed to the normal direction of the liquid crystal layer and a fixed image independent of the driving circuit is displayed to a direction other than the normal direction.
According to a further aspect of the present invention, there is provided a liquid crystal display including a first liquid crystal layer displaying an image formed by a driving circuit, a second liquid crystal layer, and alignment films sandwiching the second liquid crystal layer wherein the alignment film has regions containing a visible figure, and orientations of adjacent regions are different.
According to a further aspect of the present invention, there is provided a liquid crystal display including a liquid crystal layer, a pair of substrates sandwiching the liquid crystal layer, and a driving circuit for the liquid crystal layer, wherein an image formed by the driving circuit is displayed to the front and a fixed image independent of the driving circuit is displayed to an oblique direction.
The substrate may be made of glass.
The driving circuit may be formed on the substrate, or the driving circuit may be formed separately from the substrate.
According to a further aspect of the present invention, there is provided a terminal device including a liquid crystal layer, a pair of substrates sandwiching the liquid crystal layer, and a driving circuit for the liquid crystal layer, wherein an image formed by the driving circuit is displayed to a front direction and a fixed image independent of the driving circuit is displayed to an oblique direction.
According to a further aspect of the present invention, there is provided a portable terminal device including a liquid crystal layer, a pair of substrates sandwiching the liquid crystal layer, and a driving circuit for the liquid crystal layer, wherein an image formed by the driving circuit is displayed to a front direction and a fixed image independent of the driving circuit is displayed to an oblique direction.
According to a further aspect of present invention, the alignment films in a liquid crystal display device are divided into a plurality of regions. In each of these regions, the orientation direction is different from at least some other regions so that they are viewed as dark colors (such as black) when seen from a specified direction.
This variation in the liquid crystal display device that is dependent upon viewing angle is achieved by interfacial modification of the orientation direction performed on the alignment film.
Thus, some of the regions seen in a specified color from a specified direction prevent an image displayed on a screen from being seen from a certain direction.
Moreover, a fixed image can be viewed from a specified direction, independent of the display of an image signal inputted to the liquid crystal display device.